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Then there's amiodarone ( Cordarone, Pacerone), which is both a sodium channel blocker and a potassium channel blocker. It's by far the most effective anti-arrhythmic drug available -- possibly as much as 75%, Wylie says.

But because it lingers in many parts of the body for a long time, it can have many side effects. Doctors won't usually prescribe it if you're young and likely to be treated for a long time, Whang says.

If you're on amiodarone, you'll have to have regular tests to check how well your liver, lungs, and thyroid are working.


A somewhat controversial newer drug called dronedarone (Multaq) "was designed to be like amiodarone without the side effects," Wylie says. It does have fewer side effects, but "the trials showed that it didn't keep people in sinus rhythm very well."

The drug's manufacturers say that it kept people with atrial fibrillation out of the hospital, and Wylie agrees that may be true. "It may not prevent AFib, but it might prevent some of the symptoms of AFib, perhaps by blunting fast heart rates."

"I rarely use it," he says, "but some people love it because it does make some people feel better, and after all, we're treating for symptoms."

In January 2011, the FDA reported that two people needed a transplant because of liver failure tied to dronedarone. "That didn't show up in the trials, but if we start seeing more of this, then you've got a drug that doesn't work all that well and is toxic," Wylie says.

A clinical trial of the drug was halted in July 2011 when people with permanent AFib showed twice the risk of death, stroke, and having to go to the hospital for heart failure.

And in 2013, the FDA reported it can cause shortness of breath or a cough related to lung damage.

Be mindful of these possible side effects, and call your doctor if you notice any trouble while you're taking dronedarone.

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